Impaired object identification in idiopathic childhood occipital epilepsy

To investigate whether children with epilepsy primarily affecting the occipital cortex exhibit impairment of visual object identification and to what extent such a hypothesized dysfunction is related to an interfering functional, rather than structural, process.

We studied nine children with idiopathic childhood occipital epilepsy (ICOE) and compared them to eight children with lesional posterior cortex epilepsy (PCEs) and to 60 age-matched controls. We applied an "ascendent" paradigm of object identification, using a coarse-to-fine order procedure, which gradually integrated spatial frequency information from the most blurred image to the complete figure. In children with ICOE, we explored how epilepsy-related variables might be related to object identification task.

Children with ICOE and those with PCEs needed more physical information than controls to identify visual stimuli. There was a decreasing accuracy from controls to children with ICOE and from children with ICOE to those with PCEs. Children with ICOE demonstrated slight selective impairment in visuospatial processing and those among them having experienced a higher number of seizures or in whom interictal electroencephalography (EEG) discharges had been present for a longer time, required a higher level of physical information to recognize objects.

The observation that children with ICOE performed worse than controls in object identification, although better than children with PCEs, might indicate that functional disruption caused by epileptiform EEG abnormalities and seizures, can interfere per se with perceptual processes, even in the absence of a lesion. This effect appears to be detected only by perceptual and cognitive screening.